1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device.
2. Background Art
In order to obtain a high-performance CMIS device, micropatterning of devices advances. With the micropatterning of devices, gate oxide films are reduced in thickness. when a gate electrode consists of polysilicon, a reduction in thickness of the gate oxide film disadvantageously depletes a gate electrode in switching of a gate electrode. When the thickness of the gate oxide film is lower than 1 nm, a percentage of a depletion capacity of the gate electrode to the capacity of the gate oxide film reaches 30%.
In order to cope with this problem, a technique used in a gate electrode consisting of a metal is proposed in place of a gate electrode consisting of polysilicon. For example, an FUSI (Fully-Silicide Gate) technique that completely silicides a gate electrode is known (see M. Kakumu et al., VLSI Tech. Dig. (1984), p. 30).
However, it is known that, when gate electrodes having various gate lengths or gate widths are formed on the same semiconductor substrate, all the gate electrodes cannot be easily fully silicided (see J. Kedzierski et al., IEDM Tech. Dig. (2003)). A gate electrode having a small gate length or a small gate width can be easily fully silicided due to a reverse thin-line effect. However, in contrast to this, a gate electrode having a large gate length and a large gate width tends to be silicided. In particular, since nickel has a large diffusion coefficient on an interface between the gate electrode and a side wall, the reverse thin-line effect becomes conspicuous. When a gate electrode, which is fully silicided, and a gate electrode, which is not fully silicided, are arranged on the same chip, the operation of the semiconductor device disadvantageously fluctuates.
The gate electrodes having different gate lengths or gate widths can be fully silicided by silicidation steps adapted to gate electrodes are repeated. However, such a method makes manufacturing processes cumbersome and elongates a manufacturing period. As a result, the cost of the semiconductor increases.
Therefore, a semiconductor device obtained by fully siliciding gate electrodes having different gate lengths or different gate widths to solve the above problem is desired. Further, a semiconductor device manufacturing method fully siliciding gate electrodes independent of the gate lengths or different gate widths.